The present invention relates to a manufacturing method of a thin-film structural body which includes: a substrate; and a thin-film body formed on a sacrifice film formed on the substrate and placed with a predetermined gap from the substrate after removal of the sacrifice film.
In a thin-film structural body of this type to which the present invention is applied, a stress difference is exerted between the substrate and the sacrifice film, for example, after an annealing process carried out after the formation of the sacrifice film, with the result that cracks might occur on the substrate or the sacrifice film or both of the substrate and the sacrifice film due to the stress difference.
With respect to this problem, in a conventional thin-film structural body, a TEOS (tetraethylorthosilicate) oxide film is formed on the substrate as a sacrifice film, and after a thin-film body has been formed on the TEOS oxide film, the TEOS oxide film is removed.
However, in the case when the sacrifice film is formed by the TEOS oxide film in this conventional method, the resulting problem is that a great stress difference occurs between the sacrifice film and the substrate upon thermal shrinkage.
The present invention has been devised to solve the above-mentioned problem, and an object thereof is to provide a manufacturing method of a thin-film structural body, capable of reducing a stress difference exerted between a sacrifice film and a substrate upon thermal shrinkage.
In a first aspect of a manufacturing method of a thin-film structural body according to the present invention, in a manufacturing method of a thin-film structural body which includes: a substrate (1); and a thin-film body (21, 23, 25) formed on a sacrifice film (51) formed on the substrate and placed with a predetermined gap from the substrate by the removal of the sacrifice film, the sacrifice film is formed by a silicon oxide film in which phosphorus is mixed in a value of concentration greater than 3 mol %.
According to this aspect, since the sacrifice film is formed by the silicon oxide film in which phosphorus is mixed in a value of concentration greater than 3 mol %, it is possible to reduce a stress difference exerted between the sacrifice film and the substrate upon thermal shrinkage, while suppressing a segregation of phosphorus in the silicon oxide film, and consequently to prevent the generation of cracks.
In a second aspect of the manufacturing method of a thin-film structural body according to the present invention, the value of concentration of phosphorus is set to a value that is greater than 3 mol %, and also smaller than 4 mol %.
According to this aspect, since the value of concentration of phosphorus is set to a value that is greater than 3 mol %, and also smaller than 4 mol %, it is possible to reduce a stress difference exerted between the sacrifice film and the substrate upon thermal shrinkage, while suppressing a segregation of phosphorus in the silicon oxide film.
In a third aspect of the manufacturing method of a thin-film structural body according to the present invention, the sacrifice film is formed by a PSG film.
According to this aspect, since the sacrifice film is formed by a PSG film having a high etching rate, it is possible to easily remove the sacrifice film through an etching process.
In a fourth aspect of the manufacturing method of a thin-film structural body according to the present invention, the sacrifice film is formed by a BPSG film.
According to this aspect, since the sacrifice film is formed by a BPSG film having a high etching rate, it is possible to easily remove the sacrifice film through an etching process.
Moreover, it is possible to improve the reflow property of the sacrifice film by the effect of boron mixed into the BPSG film.
In a fifth aspect of the manufacturing method of a thin-film structural body according to the present invention, the substrate forms a sensor substrate installed in an acceleration sensor, and the thin-film body forms at least one portion of a sensor unit (3) which is installed in the acceleration sensor and which has a function of detecting the acceleration.
According to this aspect, it is possible to prevent cracks from generating in the manufacturing process of the sensor unit of the acceleration sensor.
These and other objects, features, aspects and advantages of the present invention will become more apparent in conjunction with the following detailed description and the accompanying drawings.